The present invention is directed to novel crystalline complexes of baccatin III with imidazole, 2-methylimidazole or isopropanol which are useful for isolating and purifying baccatin III from a crude plant cell culture solution. The complex is also useful for isolation and purification of baccatin III from crude extracts of bark and leaves of the plant, such as Taxus bevifolia (Western yew) Taxus baccata etc, which contain baccatin III with other impurities or from plant tissue culture (PTC) solutions.
The taxane family of terpenes, of which baccatin III is a member, is of considerable importance, since the latter is a starting material for the semi-synthesis of paclitaxel (Taxol.RTM.). Paclitaxel (Taxol.RTM.) is now considered one of the most promising treatments for breast and ovarian cancer. Its effectiveness is also demonstrated against lung cancer and melanoma.
The isolation of baccatin III from the Yew needles has been described in U.S. Pat. Nos. 9,330,696, 930,312. According to the method of these U.S. Pat. Nos. 9,330,696, 930,312, Yew needles are dewaxed with a critical or nearly critical fluid, followed by extraction of the taxoids with a mixture of critical or nearly critical fluid and a polar solvent and the resulting extract is chromatographed. The chromatography is carried out using two columns. The first column, a normal-phase silica absorption column, retains the taxoids and the second column, a reverse-phase absorption column, separates the taxoids. The taxoids, such as taxol, baccatin III, 10-deacetylbaccatin III and cephalomannine, are eluted with a mixture of critical or nearly-critical fluid and a polar solvent. Patents describing the production of baccatin III and paclitaxel PTC solutions are U.S. Pat. No. 5,407,816 and U.S. 5,637,484.
Another method for the isolation of baccatin III has been described in J. Liq, chromatogr., 12 (11), 2117-32 (1989). In this method, large quantities of methanol extracts derived from the bark of the Western yew, Taxus brevifolia and containing a mixture of five taxanes was resolved on adsorbent types (cyano and Ph bonded silica gel phases) using isocratic and gradient elution. The five taxanes obtained were, namely, Taxol, cephalomannine, 10-deacetylcephalomannine, baccatin III and 10-deacetylbaccatin III.
In addition, an improved method for isolating Taxol and certain clinically important analogs of Taxol including baccatin III has been described in U.S. Pat. No. 5,475,120. The improved method which comprises treating the crude extract of a naturally occurring Taxus species by reverse phase liquid chromatography on an adsorbent, causing the taxol and taxol analogs to be adsorbed on the adsorbent and recovering the taxol and its analogs from the adsorbent by elution with an eluant. The compounds isolated were taxol, 10-deacetylbaccatin III, baccatin III etc.
Thus, all of the above processes require an alcoholic extract or a polar solvent extract obtained from the bark or needles of the Taxus species and then chromatographing the crude extract on a column of silica gel.